arm64: dts: rockchip: Fix wrong rt5514 dmic delay property for Gru

According to rt5514 dt-binding, it should be "realtek,dmic-init-delay-ms".

Fixes: 48f4d979

 (arm64: dts: rockchip: add Gru/Kevin DTS)
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>